1. Field of the Invention
The present invention relates to an organic electroluminescent display device (and method for fabricating the same), and more particularly to a rear emitting type organic electroluminescent display device having improved luminance and emission efficiency. These advantages may be obtained by forming light emitting elements in a projecting structure in such a way that a second electrode surrounds an organic layer.
2. Description of Related Art
Organic electroluminescent display devices have received recent attention because of their merits with regard to thinness, width of viewing angle, weight, size, response speed and power consumption in comparison to cathode ray tube (CRT) and liquid crystal display (LCD) devices. Particularly, organic electroluminescent display devices may have the advantage of being easily fabricated through a simple fabrication process. The simplified fabrication process may arise from the simple structure of an organic electroluminescent display device: anode electrode, organic material film, and cathode electrode.
A brief description of a rear emitting type organic electroluminescent display follows with reference to FIG. 1.
FIG. 1 is a cross sectional view for showing a conventional rear emitting type organic electroluminescent display device.
As shown in FIG. 1, first electrode 150 may be electrically connected to the thin film transistor and may function as an anode electrode. First electrode 150 may be formed on a lower insulating substrate 100 equipped an inter-insulating layer 140 on the thin film transistor T including activation layer 110, gate electrode 120, and source/drain electrodes 131 and 135.
An opening part 165 for exposing a part of first electrode 150 may be formed by creating a pixel defined layer 160 on the front side of the lower insulating substrate 100 and using a photolithography technique on pixel defined layer 160 after forming first electrode 150.
An organic layer 170 may be formed on an upper part of an opening part 165 after forming opening part 165. Open part 165 may expose a part of first electrode 150.
An organic emitting device E including first electrode 150, organic layer 170, and a second electrode 180 may be formed by creating second electrode 180 on the front side of the lower insulating substrate 100 after forming the organic layer 170. Second electrode 180 may function as a cathode electrode.
The lower insulating substrate 100 including the thin film transistor T and organic emitting device E may be sealed using a sealing substrate as an upper insulating substrate. The sealing substrate has been omitted from the drawings, but may be formed after forming the organic emitting device E.
Unfortunately, only about 20% of light actually generated from the organic layer 170 may be extracted to the outside since the light may be lost by being absorbed by several films of a lower part of the organic layer 170 in the process of being emitted from the organic layer 170. A particularly large amount of light may be lost at one side from the first electrode 150 functioning as an anode electrode. The loss may be through total reflection. For example, a conventional rear emitting type organic electroluminescent display device may have problems with low emission efficiency and luminance because a large amount of light emitted from the organic layer 170 may be lost.